New Projects Arduino Uno

Hi, I'm new to the forum, and I'm hooked Much to the Arduino, solo What I can not find a valid project.
Can you recommend a valid Project Achieve? I was interested in a 3D printer, but They cost Very pieces. I would like to Create Something useful, but at the same time fun and cheap.
Thank you

What did you have in mind for 'useful' ? A game that you and your coworkers/friends/family can play with lights & buzzers & switches? Something that can move around by itself? Some kind of home automation? Some kind of data logging?

something that can move by itself, like a robot, but not a simple avoids obstacles, something more cute, feasible as recycled materials

Okay, so start by finding some motors, motor drivers, wheels or treads, get those working with the Arduino on whatever you decide to use as a chassis to hold it all together. There are sites like www.mpja.com and www.surplussales.com that sell parts that are recycled/reclaimed from other equipment.

Add sensors.

A visual project with coloured leds is always compelling.

There is an on-line tutorial to follow step by step to the realization?

No, only the various pieces until you define better what you are making better.

And what type is robot I realize, for example Avoid Obstacles, etc ...